The effects of obesity surgery on bone metabolism: what orthopedic surgeons need to know.

Morbid obesity affects approximately 9 million Americans. Obesity is associated with a reduced risk of osteoporosis, whereas weight loss decreases bone density. Obesity surgery has profound effects on bone, which are well described in the gastrointestinal literature; yet, there are virtually no reports in the orthopedic literature. The Roux-en-Y procedure is the leading bariatric operation performed in the United States. In this surgery, the primary sites for calcium absorption are bypassed. Patients become calcium- and Vitamin D-deficient, and the body then up-regulates parathyroid hormone, causing increased production of Vitamin D and increased calcium resorption from bone. Gastric banding utilizes a restrictive band and has not been shown to produce the same bone loss as the Roux-en-Y procedure, nor has there been evidence of secondary hyperparathyroidism. It is important for orthopedists to be aware of the types of obesity surgery and their sequelae on bone, as this may impact bone density, fracture risk, and fracture healing.